FIG. 1 is a block diagram of an example prior art magnetic disk drive system 100 having a hard disk assembly 104 and a hard disk control system 108. The hard disk assembly 104 includes one or more magnetic disks 112 and one or more corresponding magnetic heads 116 on a moving arm 120. The moving arm 120 is coupled to an actuator 124 that is used to position the magnetic heads 116 over the magnetic disks 112. The hard disk control system 108 includes an interface 128 that receives data to be written to the one or more magnetic disks 112 and transmits data read from the one or more magnetic disks 112. The interface 128 is communicatively coupled to a microprocessor of a computing system such as a server, a personal computer, a network attached storage (NAS) device, etc., or of a consumer electronics device such as a smart phone, a set top box, a gaming system, etc., to allow the microprocessor to store data to and read data from the one or more magnetic disks 112. The interface 128 is coupled to a hard disk controller (HDC) 132. The HDC 132 is in turn coupled to a read channel device 136, a write channel device 138, and an actuator controller 140. The read channel device 136 and the write channel device 138 are coupled to the magnetic heads 116. The actuator controller 140 is coupled to the actuator 124. Optionally, the read channel device 136 and/or the write channel device 138 are coupled to the actuator controller 140.
Data to be written to the disks 112 are received via the interface 128. The HDC 132 transmits signals to the actuator controller 140 indicating the disk and the track on which data is to be written. During positioning, the read channel device 136 reads position signal information from the appropriate disk 112 and provides this position signal information to the actuator controller 140. The actuator controller 140 uses the position signal information from the read channel device 136 to accurately position the appropriate magnetic head 116 to the desired track. Meanwhile, the HDC 132 provides the data to be written to the write channel device 138. Once the magnetic heads 116 are appropriately positioned, the write channel device 138 generates an analog write signal and provides the analog write signal to the appropriate magnetic head 116 such that the data is magnetically stored on the disk 112 at the desired position.
When data is to be read from one of the disks 112, the microprocessor of the computing device or consumer electronics device provides a request to the interface 128, indicating the data to be read. The interface 128 provides the indication to the HDC 132. Then, the HDC 132 transmits signals to the actuator controller 140 indicating the disk and the track from which data is to be read. During positioning, the read channel device 136 generates position signals based on position information written on the disk 112 and provides these position signals to the actuator controller 140. The actuator controller 140 uses the position signals to accurately position the magnetic head 116 to a center of a desired track. Additionally, the HDC 132 indicates to the read channel device 136 from which of the disks 112 (if there are multiple disks) to read and when to begin reading so that data from an appropriate portion on the disk 112 will be read. In response, at the appropriate time, the read channel device 136 generates a digital signal from an analog signal received from the magnetic head 116. This digital signal is provided to the HDC 132. The HDC 132 provides the retrieved data to the interface 128, which in turn provides the retrieved data to the requesting microprocessor.
FIG. 2 is an illustration of an example magnetic media disk 150 that is utilized in the disk drive system 100 of FIG. 1. The disk 150 includes a plurality of servo field areas 154 that generally radiate outwardly from the center of the disk 150. Each servo field area 154 is generally wedge shaped. Additionally, the disk 150 is generally partitioned into a plurality of concentric regions referred to as tracks 158. A servo field area 154 within a particular track 158 is sometimes referred to as a servo mark. Each servo mark includes data which is pre-written on the disk 150 during manufacturing, and such data includes data concerning the location of the servo mark on the disk 150, such as the particular servo field area to which the servo mark corresponds and the track in which the servo mark is located. As can be seen in FIG. 2, each track 158 includes several servo marks. The servo mark data is used by the hard disk system to position the magnetic head 116 during read and write operations. Data to be stored is written in the tracks 158 between the servo fields.
Referring again to FIG. 1, a frequency at which bits are written to the disk 112 (write frequency) is typically offset from a frequency of a clock used by the read channel device 136. Such a frequency offset adversely affects the reading of data from the disk 112.
Additionally, when the magnetic head 116 is positioned over a particular track, the magnetic head 116 will typically generate an interference signal from an adjacent track (sometimes referred to as “intertrack interference”). Such intertrack interference also adversely affects the reading of data from the disk 112.
Further, other technical limitations of the read channel device 136, the write channel device 138, and/or the magnetic head 116 can further adversely affect the reading of data from the disk 112. For example, asymmetry corresponding to an amplitude difference between positive peaks and negative peaks in a readback signal (which may be caused by characteristics of the magnetic head 116) will also adversely affect the reading of data from the disk 112.